1. Field of the Invention
The present invention is related to a plasma display panel, and particularly to a method and apparatus for driving a plasma display panel, which reduces dark areas on the display panel by a new arrangement of the polarities of the scanning and sustaining electrodes during the sustaining discharge.
2. Description of the Related Art
A conventional plasma display panel 10 is schematically shown in FIG. 1. The plasma display panel 10 comprises display lines L1xcx9cL600 and addressing electrodes A1xcx9cA400. The display lines L1xcx9cL600 comprise pairs of scanning and sustaining electrodes (X1, Y1)xcx9c(X600, Y600) respectively. The scanning and sustaining electrodes (X1, Y1)xcx9c(X600, Y600) are disposed in parallel with each other and orthogonal to the addressing electrodes A1xcx9cA400. Areas 11 between the scanning and sustaining electrodes (X1, Y1)xcx9c(X600, Y600) are luminous areas where sustaining discharge is carried out. On the other hand, areas 12 between two neighboring display lines (i.e., areas between the two neighboring electrodes of two respective display lines) are dark areas where no sustaining discharge is carried out.
FIG. 2 is a timing diagram showing a subframe of a conventional method for driving the plasma display panel 10 shown in FIG. 1. In practice, it takes several subframes, 8 for example, to show a complete image for one frame. In FIG. 2, each subframe comprises periods of reset, scanning and sustaining discharge. All the display lines of the plasma display panel 10 are reset during the reset period and display data is written to all display cells (not shown) of the display plasma panel 10 by the addressing electrodes A1xcx9cA400 during the scan period. The sustain discharge period will be explained in detail. During the sustain discharge period, a driving pulse 21 is applied to the scanning electrodes X1xcx9cX600 and alternately, a driving pulse 22 is applied to the sustaining electrodes Y1xcx9cY600. Thus, the discharge therebetween is maintained for sustained emission of light. More specifically, in the plasma display panel 10, all the scanning electrodes X1xcx9cX600 have the same applied voltage and the same polarity because they are connected together. Correspondingly, by the applied driving pulses 22, the polarities of all the sustaining electrodes Y1xcx9cY600 are also the same but opposite to those of the scanning electrodes X1xcx9cX600 during the sustaining discharge. This results in wall charges accumulated in a MgO film over the scanning electrodes X1xcx9cX600 and the sustaining electrodes Y1xcx9cY600 of the display lines L1xcx9cL600.
FIG. 3 schematically shows the polarities of the scanning and sustaining electrodes and the induced wall charges during the sustain discharge period within a subframe applying the conventional method. It is noted that the polarities of the sustaining electrode YNxe2x88x921 and YN of the display line LNxe2x88x921 and LN are positive, which are opposite to those of the scanning electrode XN and XN+1 of the neighboring display line LN and LN+1, which are negative. Namely, each two of the neighboring electrodes of two respective display lines are opposite in polarity during the sustaining discharge. Therefore, the polarities of the wall charges accumulated in a MgO film 30 over the scanning electrodes X1xcx9cX600 and the sustaining electrodes Y1xcx9cY600 are in, for example, the order of xe2x88x92, +, xe2x88x92, +, xe2x88x92, . . . , xe2x88x92 or in the order of +, xe2x88x92, +, xe2x88x92, . . . , +, xe2x88x92. This may results unexpected discharge in the dark area 12 between each two of the neighboring display lines when the distance therebetween is short enough. Consequently, in the conventional method, there is a need for a sufficiently large dark area that disadvantageously reduces the luminance of images shown by the display plasma panel.
To eliminate the above problem, a method for driving a plasma display panel is provided in U.S. Pat. No. 5,420,602, which reduces the dark area and also avoids the unexpected discharge.
FIG. 4 schematically shows the polarities of the scanning and sustaining electrodes and the induced wall charges during the sustaining discharge within a subframe applying the method provided in U.S. Pat. No. 5,420,602. It is noted that the disposition of the scanning and sustaining electrodes is different from that of FIG. 3. In FIG. 4, the scanning and sustaining electrodes are disposed in the order of (XNxe2x88x921, YNxe2x88x921), (YN, XN), (XNxe2x88x921, YN+1) Namely, each two of the neighboring electrodes of two respective display lines are identical in polarity during the sustaining discharge. Such disposition results in a new arrangement of the polarities of the induced wall charges in the MgO film 30 over the scanning and sustaining electrodes. The polarities of the induced wall charges are in the order of +, xe2x88x92, xe2x88x92, +, +, xe2x88x92. Therefore, the unexpected discharge no longer occurs even in a small dark area.
However, in the method provided in U.S. Pat. No. 5,420,602, there is a need for reconstruction of the plasma display panel for the above-mentioned disposition of the scanning and sustaining electrodes, which disadvantageously increases the complexity of the peripheral circuit.
A method and apparatus for driving a plasma display panel are provided in the present invention, which reduces the dark area and avoids the unexpected discharge without the need for reconstruction of the plasma display panel.
One of the objects of the invention is to provide a method for driving a plasma display panel comprising the steps of reset, scanning and sustaining discharge. The plasma display panel has display lines comprising scanning electrodes and sustaining electrodes disposed in parallel with each other, and addressing electrodes extending orthogonally to the scanning and sustaining electrodes. The method is characterized in that the step of sustaining discharge is carried out by alternately applying a first driving pulse to the two scanning electrodes of each pair of the neighboring display lines and a second driving pulse to the two sustaining electrodes of each pair of the neighboring display lines so that each two of the neighboring electrodes of two respective display lines are identical in polarity during the sustaining discharge.
Another one of the objects of the invention is to provide an apparatus for driving a plasma display panel. The plasma display panel has odd-numbered and even-numbered display lines both comprising scanning electrodes and sustaining electrodes disposed in parallel with each other, and a plurality of addressing electrodes extending orthogonally to the scanning and sustaining electrodes. The apparatus comprises a first, second, third and fourth driver. The first driver alternately applies a high and low voltage level to the sustaining electrodes of the odd-numbered display lines. The second driver alternately applies the high and low voltage level to the sustaining electrodes of the even-numbered display lines. The third driver alternately applies the high and low voltage level to the scanning electrodes of the odd-numbered display lines. The fourth driver alternately applies the high and low voltage level to the scanning electrodes of the even-numbered display lines. Thereby, during the sustaining discharge of the plasma display panel, the high voltage level is applied to the scanning electrodes of the odd-numbered display lines and the sustaining electrodes of the even-numbered display lines when the low voltage level is applied to the sustaining electrodes of the odd-numbered display lines and the scanning electrodes of the even-numbered display lines, and the low voltage level is applied to the scanning electrodes of the odd-numbered display lines and the sustaining electrodes of the even-numbered display lines when the high voltage level is applied to the sustaining electrodes of the odd-numbered display lines and the scanning electrodes of the even-numbered display lines.
Accordingly, during the sustain discharge period, each two of the neighboring electrodes of two respective display lines are identical in polarity, which results from the timing of the applied driving pulses instead of disposition of the scanning and sustaining electrodes. Therefore, there is no need for reconstruction of the plasma display panel in the invention.